What are warning signs at 18 weeks pregnant?

Severe abdominal or one-sided pelvic pain with bleeding — possible ectopic pregnancy.; Heavy vaginal bleeding (soaking a pad in an hour) with cramping.; Fainting, severe dizziness, or shoulder-tip pain — ectopic with internal bleeding is an emergency.; Fever over 101°F with chills or pelvic pain.; Severe vomiting that prevents keeping any fluids down for 24+ hours (hyperemesis).;

Second trimester · Pregnancy week by week

Week 18 of pregnancy

Q: How big is the baby at 18 weeks?

size of a bell pepper. Fetal sex is clearly visible on ultrasound. The fetus is more active — yawns, stretches, hiccups. Auditory pathways are developing. Some women report a clear pattern of activity (more active at night).

Baby is the size of a bell pepper. About 5.60 inches, 200g.

Week 18 is anatomy-scan window. Per ACOG, the detailed anatomy survey at 18–22 weeks identifies 70% of fetal anomalies. Black women are referred to MFM (maternal-fetal medicine) for abnormal findings 15% less often per documented disparity literature. Source

What's happening with the baby

Fetal sex is clearly visible on ultrasound. The fetus is more active — yawns, stretches, hiccups. Auditory pathways are developing. Some women report a clear pattern of activity (more active at night).

What's happening for you

Pregnancy is obvious. Many women feel kicks daily. Lower back pain, leg cramps (especially at night), and constipation increase. Some experience varicose veins or hemorrhoids for the first time.

Common (normal) symptoms this week

Regular fetal movements, leg cramps at night, lower back pain, hemorrhoids or varicose veins, occasional dizziness, sensitive skin, vivid dreams.

Call your OB or 911 if

Severe abdominal or one-sided pelvic pain with bleeding — possible ectopic pregnancy.
Heavy vaginal bleeding (soaking a pad in an hour) with cramping.
Fainting, severe dizziness, or shoulder-tip pain — ectopic with internal bleeding is an emergency.
Fever over 101°F with chills or pelvic pain.
Severe vomiting that prevents keeping any fluids down for 24+ hours (hyperemesis).

Why this week matters for Black families

The second trimester is when the standard prenatal-care path diverges most sharply by demographic. The 20-week anatomy scan, the preeclampsia-prevention conversation, and the gestational-diabetes screening all happen here. Black women have higher rates of gestational diabetes, fibroids that complicate pregnancy, and a documented risk of missed preeclampsia diagnoses because early symptoms (headache, swelling, vision changes) are dismissed more often (per Bryant 2010 Obstet Gynecol PMID 20567176). If you have any of these symptoms, name them and ask explicitly: 'Has preeclampsia been ruled out?'

What to do this week

Anatomy scan typically happens this week or next. Bring a notebook and ask: 'Is everything normal? Any concerns about heart, brain, spine, kidneys, abdomen, limbs?' Document any flagged findings. If anything is abnormal, ask for an MFM referral. Continue weekly self-care.

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References

ACOG Practice Bulletin 175 — Ultrasound in Pregnancy.
SMFM Anatomy Survey Standards.

Last medically reviewed: April 25, 2026.

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